This invention relates to pumps, and, more particularly, to pumps having highly-accurately controlled dosing.
Highly-accurate pumps are known in the prior art for repeatedly delivering doses within exacting tolerances, even at extremely low-dose volumes. For example, with reference to International Patent Application No. PCT/US00/23206, published as International Publication No. WO 01/14245 on Mar. 1, 2001, a pre-compression pump system is shown for repeatedly delivering microdoses of fluid. The pump of this design utilizes a stationary seal which bears against a moving valve stem. The stroke of the pump is defined by the length of a constant-diameter portion of the valve stem which terminates at a lower extreme defined by a plurality of circumferentially-spaced recesses. In this manner, the seal member remains in constant sealing engagement with the valve stem with fluid bypassing the sealing member via the recesses to re-charge the pump chamber. With this structural configuration, accurate control of dosing can be achieved through accurate dimensioning of the valve stem and recesses. In a different approach, U.S. Pat. No. 5,277,559, which issued on Jan. 11, 1994 to the inventor herein, a pump with a sliding seal is provided which moves, at least in part, with a valve stem that selectively controls flow through the pump.
With the subject invention, pump systems are provided which allow for highly-accurate dose control. In one embodiment, a pump system is provided which includes a pump body having a first chamber defined therein; a valve stem disposed to slide within at least a portion of the pump chamber, the valve stem having a constant-diameter stroke portion interposed between reduced-diameter portions; and at least one stationary sealing member immovably affixed to the pump body formed to sealingly engage the stroke portion of the valve stem. The sealing member is also formed to not engage the reduced-diameter portions of the valve stem. With the sealing member sealingly engaging the stroke portion of the valve stem, a portion of the first chamber of the pump body is isolated or substantially isolated from other portions of the chamber. Accordingly, fluid trapped within the first portion may be compressed and dispensed.
In a second embodiment, a pump system is provided which includes a pump body having a first chamber defined therein; a piston disposed to slide within at least a portion of the first chamber, the piston having a constant-diameter stroke portion interposed between reduced-diameter portions; and at least one stationary sealing member immovably affixed to the pump body formed to sealingly engage the stroke portion of the piston. The sealing member is also formed to not engage reduced-diameter portions of the piston. With the sealing member sealingly engaging the stroke portion, a portion of the first chamber is isolated or substantially isolated from other portions of the first chamber. Again, as with the first embodiment, fluid trapped within the first chamber can be pressurized in being dispensed.
With both embodiments, the volume of the administered dose is controlled by the stroke length, which, in turn, is a function of the dimensioning of the constant-diameter stroke portion and the dimensioning of the sealing member. Advantageously, with the subject invention, a minimal number of tolerances can be implicated in controlling dosing volume.
In third and fourth embodiments, xe2x80x9cin-linexe2x80x9d pump systems can be provided having an exit aperture extending along the longitudinal axis of the pump system (such as in the manner of a nasal spray). These embodiments each include a valve stem and operate in the same basic manner as the first embodiment.
These and other features will be better understood through a study of the following detailed description and accompanying drawings.